We report the reaction of 4,4′-substituted benzils with squaramides (SQ) affording mono-squarimides (SQIs). The ¹H NMR and X-ray structures of the SQIs (R = H) revealed the existence of a strong C=O···HN intramolecular hydrogen-bond motif. The unprecedented reaction between SQs and benzils highlights the difference in reactivity between urea and squaramide units.